Author Who Walked with ISIS: 'They Are More Dangerous Than People Know'

A well-known author who who traveled into Islamic State territory has warned the West that the militant group is very committed to their cause, including beheadings, slavery and child fighters, and may soon invade Europe.

Juergen Todenhoefer, a German journalist who spent 10 days with the terrorist group caliphate regions of Raqqa in Syria and Mosul in Iraq, recounted his experience in an interview with CNN

"These are not stupid people,"the 74 year old said. "One of the people we met had just finished his law degree. He had great job offers, but he turned them down to go and fight. ... We met fighters from Europe and the United States. One of them was from New Jersey. Can you imagine a man from New Jersey traveling to fight for the Islamic State?"

Todenhoefer added that ISIS militants are so dedicated to the cause, they are not only willing, but eager to die on the battlefield.

"When we stayed at their recruitment house, there were 50 new fighters who came every day," he said, CNN reported. "And I just could not believe the glow in their eyes. They felt like they were coming to a promised land - like they were fighting for the right thing."

The author recounted one instance, where he met with a child fighter wearing Islamic State attire and waving an AK-47. Although the boy claimed to be 13, Todenhoefer said he looked much younger.

Todenhoefer also recalled an interview he conducted with a German member who spoke on behalf of his Islamic State leadership.

"We will conquer Europe one day," the man said. "It is not a question of 'if' we will conquer Europe, just a matter of 'when' that will happen. But it is certain. ... For us, there is no such thing as borders. There are only front lines. Our expansion will be perpetual. ... and the Europeans need to know that when we come, it will not be in a nice way. It will be with our weapons. And those who do not convert to Islam or pay the Islamic tax will be killed."

However, "there is [now] an awful sense of normalcy in Mosul," Todenhoefer said.

"130,000 Christians have been evicted from the city, the Shia have fled, many people have been murdered and yet the city is functioning and people actually like the stability that the Islamic State has brought them," he said.

"Of course many of the them are quite scared, because the punishment for breaking the Islamic State's strict rules is very severe," he added.

When Todenhoefer asked the fighter about their treatment of religious minorities, including Christians, Yazidi, and Shia Muslims, the militants expressed an unwavering belief that all of those who refuse to convert to their religion must be killed.

"150 million, 200 million or 500 million, it does not matter to us," the fighter answered. "We will kill them all."

"Slavery absolutely signals progress," the ISIS fighter explained regarding the group's treatment of captives. "Only ignorant people believe that there is no slavery among the Christians and the Jews. Of course there are women who are forced into prostitution under the worst circumstances. I would say that slavery is a great help to us and we will continue to have slavery and beheadings, it is part of our religion... many slaves have converted to Islam and have then been freed."

In concluding his interview, Todenhoefer issued a serious warning to the U.S. and other Western powers, urging government leaders to take the terrorist group very seriously, as they are "entrenched" in the areas they have invaded.

"I think the Islamic State is a lot more dangerous than Western leaders realize," he said. "They believe in what they are fighting for and are preparing the largest religious cleansing campaign the world has ever seen."